Method of tubing manufacturing

ABSTRACT

A method of tubing manufacture comprising forming a tube having an internal artifact projecting radially inward from a tube inner surface, retaining the tube in a fixture, broaching an end of the tube to remove a longitudinal portion of the internal artifact which longitudinal portion is less than a total length of the tube, finishing the radius of the internal artifact so it is substantially equal to a radius (R 1 ) of the adjacent inner surface, and forming a single flare on the end of the tube.

FIELD OF THE INVENTION

The invention relates to a method of tubing manufacturing, and more particularly, to a method of tubing manufacturing comprising broaching a tube to remove a longitudinal portion of an internal artifact which longitudinal portion is less than the total length of the tube, and a finished radius of the internal artifact is substantially equal to a radius of the adjacent inner surface.

BACKGROUND OF THE INVENTION

Generally, broaching is a metal manufacturing process by which a metal blank is formed to a final or near final shape by use of a die. The metal blank can either be pressed or pulled through the die, and can move either linearly or in a rotary motion. Passing the metal blank through the die cuts the metal blank to the desired final shape.

Broaching can be used to form either an interior or an exterior surface. Forming an exterior surface of a workpiece is also called pot broaching.

Blind broaching refers to use of a broach which does not pass completely through the work piece, but instead extends only partially into the piece. Blind broaching is typically applied in situations where only a short throw is required, hence it is not used when machining multi-foot lengths of tube and pipe.

Tubing and pipe can be made using a number of methods which include seam welding. Seam welded tubing comprises rolling flat stock into a round shape, and then joining the adjacent edges by welding. The welding process will typically leave a weld bead and slag. The weld bead or slag may need to be removed depending on the intended use of the tubing. The weld bead or slag can interfere with fluid flow or the intended method of endforming terminations for joining lengths of the tubing to each other.

Endforming terminations directly on tubing allows a manufacturer to produce a leak-free connection for hydraulic systems. In order to create proper terminations, a manufacturer may create physical interferences between a punch, the tubing, and a set of clamping blocks. This reduces the cost of brazing or-welding the terminations on the tubing ends. However, while endforming is often more cost effective than welding or brazing, endforming often requires the use of drawn-over-mandrel (DOM) tubing instead of less costly non-DOM material. Non-DOM tubing is much more cost effective, but is not allowed for certain termination styles due to an internal weld seam being present. The weld seam has a negative impact on sealing performance, as the effected sealing surface may leak in the weld seam area through a weld undercut.

Representative of the art is U.S. Pat. No. 6,887,020 which discloses a device for deburring the inside of a longitudinally seam-welded pipe includes a retention arm secured outside the pipe in the area of the pipe that is not yet closed and having an end zone which is located behind the welding spot. Arranged on the retention arm is a frame part which is tiltable in longitudinal direction of the pipe about a tilt axis and provided with a scraping tool. The tilt axis of the frame part is hereby located, as viewed in advancing direction, behind the scraping point at the end of the frame part. An adjustment mechanism is provided on the forward end of the frame part for adjusting the tilt angle.

What is needed is a method of tubing manufacturing comprising broaching the tube to remove a longitudinal portion of an internal artifact which longitudinal portion is less than the total length of the tube, and a finished radius of the internal artifact is substantially equal to a radius of the adjacent inner surface. The present invention meets this need.

SUMMARY OF THE INVENTION

The primary aspect of the invention is to provide a method of tubing manufacturing comprising broaching the tube to remove a longitudinal portion of an internal artifact which longitudinal portion is less than the total length of the tube, and a finished radius of the internal artifact is substantially equal to a radius of the adjacent inner surface.

Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.

The invention comprises a method of tubing manufacture comprising forming a tube having an internal artifact projecting radially inward from a tube inner surface, retaining the tube in a fixture, broaching an end of the tube to remove a longitudinal portion of the internal artifact which longitudinal portion is less than a total length of the tube, finishing the radius of the internal artifact so it is substantially equal to a radius (R1) of the adjacent inner surface, and forming a single flare on the end of the tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part of the specification, illustrate preferred embodiments of the present invention, and together with a description, serve to explain the principles of the invention.

FIG. 1 is a cross section of a single flared tubing end.

FIG. 2 is a cross section of a double-flared tubing end.

FIG. 3 is a cross section of a broached tube.

FIG. 4 is an end view of a tube.

FIG. 5 is a detail of FIG. 4.

FIG. 6 is a cross section of a single flare coupling.

FIG. 7 is a perspective view of the punch mechanism.

FIG. 8 is a side view of the punch.

FIG. 9 is an exploded view of the punch mechanism.

FIG. 10 is a cross sectional view of the inventive device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a cross section of a single flared tubing end. Tubing 10 is shown with an end 11 having a single flare. Flaring is accomplished using methods known in the art, for example by use of a mandrel. The tubing comprises a weld bead 13, see FIG. 5. In certain applications the weld bead is known to provide a leak path which prevents use of the tubing under certain industry standards.

The angle α of the flare may be in the range of 35° to 90°, allowing for use in a wide range of applications. For example, a flare angle of 37° is well suited for certain coupling applications.

FIG. 2 is a cross section of a double-flared tubing end. Tubing 10 is shown with a double flared end 11, 12. The double flare is accomplished using methods known in the art, for example by use of a mandrel. The double flare end comprises a portion of the single flare end, see FIG. 1, which is rolled back on itself.

As shown in FIG. 1 and FIG. 2, tubing 10 comprises a weld bead 13. Weld bead 13 is typically the result of electric resistance welding, flash controlled, and then normalized by post weld heat treatment. The process is typically used on single wall, low carbon steel pressure tubing and is more fully described in SAE Standard J356. The manufacturing process is intended to make tubing for use in pressure lines and other applications which require tubing of a quality suitable for bending, double flaring, beading, forming and brazing. Tubing manufactured to the J356 standard is not intended for “single flare” applications due to the potential leak path caused by the ID weld bead 13, see FIG. 4.

FIG. 3 is a cross section of a broached tube. Tube 10 is made according to standard J356 with an internal weld bead 13. According to the invention, a longitudinal portion of the inwardly projecting weld bead 13 is shown removed by a linear broach over a distance D1 from the end of the tube. Distance D1 is at least equal to or greater than a length of radius R1, see FIG. 4. Distance D1 must be sufficient to allow either a single or a double flare to be applied to the end of the tube without either flare engaging the inwardly projecting portion of the weld seam 13. An end 14 of the weld bead 13 can be chamfered at an angle (α2) to aid fluid flow.

A finished radius of the broached weld seam 13 is substantially equal to a radius (R1) of the adjacent internal surface 15. That is, the surface of the broached weld seam blends with the surface of the adjacent tube inner surface 15. The broach stroke is of a depth sufficient to remove the projecting weld seam plus any undercut in the weld seam which may otherwise provide a leak path.

The inventive method can be used to make tubing manufactured under SAE J356 compliant with SAE J525 for single flare use.

In an alternative method the tubing may be machined or turned using a cutting tool to remove the inward projecting weld bead up to a distance D1.

FIG. 4 is an end view of a tube. Tube 10 comprises an inner surface 15 having radius R1.

FIG. 5 is a detail of FIG. 4. Weld seam 13 comprises, for example, dimensions of approximately a=0.08 mm by b=0.08 mm. Weld filler material 16 is applied during tube manufacture.

FIG. 6 is a cross section of a single flare coupling. Compression nut 18 is threaded to body 19. The flared end is compressed between nut 18 and body 19. Bush 17 distributes the clamping force on end 11 to ensure a better seal with body 19. O-ring 20 acts as a seal when attaching body 19 to another piece of tubing. Threads 21 are a known means of attaching body 19 to another piece of tubing, or, to another fitting.

FIG. 7 is a perspective view of the punch mechanism. Punch mechanism comprises base 200, collar 201, collar 202, body 203, punch 300 and spring 204. Punch 300 slides within collar 201 and 202. Punch 300 is driven into the workpiece by base 200. Body 203 aligns and guides the punch relative to the workpiece. Spring 204 retracts the punch from the workpiece.

FIG. 8 is a side view of the punch. Punch 300 comprises cylindrical portion 301 which removes the weld bead from the interior of the tube during the broaching operation. Cylindrical portion 301 and mounted to body portion 302. Body portion 302 engages collars 201 and 202.

FIG. 9 is an exploded view of the punch mechanism. Spring 204 comprises a coil spring. Body 200 may be mounted within a hydraulic ram (not shown) known in the art. During the broaching operation, the workpiece (tube) is clamped in a fixture. Coil spring 204 retracts punch 300 from tube 10 after the broaching operation is complete.

FIG. 10 is a cross sectional view of the inventive device. Tube 10 is rigidly fixed in a clamping fixture 400. A bore of fixture 400 may comprise ribs 401 in order to better grip tube 10 during the broach process.

Method.

The tubing is typically manufactured according to SAE Standard J356, but may also be manufactured using any method which results in a weld bead on an inner surface. The method of tubing manufacture comprises forming a tube having an internal artifact, namely a weld bead, projecting radially inward from a tube inner surface. Tube 10 is then clamped in a fixture 400. A linear broach of the tube is performed using punch 300 to remove a longitudinal portion of the internal artifact which longitudinal portion is less than a total length of the tube. The radius of the internal artifact after the broach is substantially equal to a radius (R1) of the adjacent inner surface. A single flare is then applied to the broached end of the tube. The single flare may be used with single flare tube fittings.

All numeric values provided herein are by way of example only, and are not intended to limit the scope of the invention.

Although a form of the invention has been described herein, it will be obvious to those skilled in the art that variations may be made in the construction and relation of parts without departing from the spirit and scope of the invention described herein. 

I claim:
 1. A method of tubing manufacture comprising: forming a tube having an internal artifact projecting radially inward from a tube inner surface; retaining the tube in a fixture; broaching an end of the tube to remove a longitudinal portion of the internal artifact which longitudinal portion is less than a total length of the tube; finishing the radius of the internal artifact so it is substantially equal to a radius (R1) of the adjacent inner surface; and forming a single flare on the end of the tube.
 2. The method of tubing manufacture as in claim 1 comprising extending the broach within the tube for a longitudinal distance that is at least greater than a radius of the tube.
 3. The method of tubing manufacture as in claim 1, wherein the internal artifact is a weld bead.
 4. The method of tubing manufacture as in claim 1, wherein the broach is linear.
 5. The method of tubing manufacture as in claim 1, wherein the weld bead is chamfered.
 6. The method of tubing manufacture as in claim 1 comprising forming a second flare in the end of the tube.
 7. A method of tubing manufacture comprising: forming a tube having a weld bead projecting radially inward from a tube inner surface; retaining the tube in a fixture; broaching the tube a longitudinal distance at least greater than a radius of the tube to remove a longitudinal portion of the weld bead, which longitudinal portion is less than a total length of the tube; finishing the radius of the weld bead so it is substantially equal to a radius (R1) of the tube; and flaring the broached end of the tube.
 8. The method as in claim 7 comprising applying a second flare to the broached end of the tube.
 9. The method as in claim 7 wherein the flare comprises an angle of approximately 37°. 